
meristemsunflower animation

Here's a growing sunflower for you (if we're lucky). More below.
(If the animation doesn't show, here
is a fullsized screen shot.)
What's a meristem?
A meristem is the tip or center of a new plant part (stem, root, leaf,
flower, fruit...) where growth of the part starts and gets its
pattern. It's something like a stemcell niche in animals: a bunch
of undifferentiated cells proliferate there, then become more
differentiated as they either spread
away from the meristem, or push the meristem ahead of themselves.
Here's the Wikipedia
article. Often, in flowers and leaf buds, but even at branch
tips, the meristem is hidden there's a little indent
like a whirlpool in the center that everything else has emerged
/ is emerging from.
This applet animates the pattern of seeds in a growing sunflower.
The process of the seed buds emerging and moving away from the
meristem, called "spiral phylotaxis," is what produces this pattern.
So I put a meristem in the center. Artist's conception.
The code
The applet was originally written for the Javabased
Processing environment.
On this page, the unchanged source code
is being run in your browser by a script from the
Processing.js project.
There's also an equivalent
Python version
to run with
PyProcessing.
More about spiral phylotaxis
The applet cheats, using the goldenratio angle. Plants don't actually
calculate the golden ratio; the pattern is
formed by seeds growing into gaps between the earlier seeds, which is
demonstrated brilliantly by S. Douady and Y. Couder in
this video.
Vi Hart has a great series of videos, "Doodling in Math Class:
Spirals, Fibonacci and Being a Plant."
Part One
Part Two
Part Three,
which gets down to the nitty gritty and a bit of debunking, and
Notes and References, where the links are rectangles that appear as the
video plays.
Hart references the short article
"The Mathematical Lives of Plants,"
by Julie J. Rehmeyer (webstyle version
here).
Steve Witham
Up to my home page.